Ethylene Polymerization Catalysis by Vanadium-Based Systems Bearing Sulfur-Bridged Calixarenes

Calixarenes bridged by thia (−S−), sulfinyl (−SO−), or sulfonyl (−SO₂−) linkers have been employed as ancillary ligands in vanadium-based ethylene polymerization and in the ring-opening polymerization of ε-caprolactone. For ethylene polymerization, all pro-catalysts [PPh₄]­[VOCl₂(R-calix­[4]­areneH₂)] (R = p-tert-butylthia (−S−) (1), sulfinyl (−SO−) (2), sulfonyl (−SO₂−) (3)) were highly active, with the system bearing the sulfonyl (−SO₂−)-bridged calixarene displaying enhanced activity. The molecular structures of pro-catalysts 2 and 3 are reported. Pro-catalysts 1–3 were inactive for the ROP of ε-caprolactone.